Thermal actuator

ABSTRACT

An improved form of thermal actuator suitable for use in a MEMS device. The actuator includes a first material such as polytetrafluoroethylene having a high coefficient of thermal expansion and a serpentine heater material having a lower coefficient of thermal expansion in thermal contact with the first material and heating the first material on demand. The serpentine heater material is elongated upon heating so as to accommodate the expansion of the first material.

FIELD OF THE INVENTION

The present invention relates to a device and, in particular, discloses a thermal actuator.

The present invention further relates to the field of micro-mechanics and micro-electro mechanical systems (MEMS) and provides a thermal actuator device having improved operational qualities.

BACKGROUND OF THE INVENTION

The area of MEMS involves the construction of devices on the micron scale. The devices constructed are utilised in many different field as can be seen from the latest proceedings in this area including the proceedings of the IEEE international workshops on micro-electro mechanical systems (of which it is assumed the reader is familiar).

One fundamental requirement of modern micro-mechanical systems is need to provide an actuator to induce movements in various micro-mechanical structures including the actuators themselves. These actuators as described in the aforementioned proceedings are normally divided into a number of types including thermal, electrical, magnetic etc.

Ideally, any actuator utilized in a MEMS process maximises the degree or strength of movement with respect to the power utilised in accordance with various other trade offs.

Hence, for a thermal type actuator, it is desirable to maximise the degree of movement of the actuator or the degree of force supplied by the actuator upon activation.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide for an improved form of thermal actuator suitable for use in a MEMS device.

In accordance with a first aspect of the present invention, there is provided a micromechanical thermal actuator comprising a first material having a high coefficient of thermal expansion and a serpentine heater material having a lower coefficient of thermal expansion in thermal contact with the first material and adapted to heat the first material on demand, wherein the serpentine heater material being elongated upon heating so as to accommodate the expansion of first material.

In accordance with a second aspect of the present invention, there is provided a micro-mechanical thermal actuator comprising a first layer having a first coefficient of thermal expansion, a second layer having a relatively higher coefficient of thermal expansion than the first layer, and a heater element in thermal contact with the first and second layers such that, on heating the heater, the actuator moves from a first quiescent position to a second actuation position. Further, the heater element comprises a serpentine layer of poly-silicon, which is sandwiched between the first and second layers. Preferably, the first layer comprises polytetrafluoroethylene, and the second layer comprises silicon dioxide or silicon nitride.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of the present invention, preferred forms of the invention will now be described, by way of example only, with reference to the accompanying drawings which:

FIG. 1 is a perspective cross-sectional view of two thermal actuators constructed in accordance with the preferred embodiment.

FIG. 2 is a cross-sectional view of a thermal actuator constructed in accordance with the another embodiment.

FIG. 3 is an exploded perspective view illustrating the construction of a single thermal actuator in accordance with an embodiment of the present invention.

DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

In the preferred embodiment, a thermal actuator is created utilising a first substance having a high coefficient of thermal expansion and a second substance having a substantially lower coefficient of thermal expansion.

Turning now to FIG. 1, there is shown one form of thermal actuator constructed in accordance with the preferred embodiment. The arrangement 1 includes an actuator arm 2 which includes a bottom field oxide layer 3 which has been etched away underneath by means of an isotropic etch of a sacrificial material underneath the field oxide layer 3 so as to form cavity 4.

On top of the field oxide under layer 3 is constructed a poly-silicon layer 5 which is in the form of a serpentine coil and is connected to two input leads 7, 8.

The poly-silicon coil 5 acts as a resistive element when energised by the input leads which further results in a heating of the poly-silicon layer 5, a corresponding heating of the field oxide 3, in addition to the heating of a polytetrafluoroethylene (PTFE) layer 10 which is deposited on the top of the poly-silicon layer 5 and field oxide 3. The PTFE layer 10 has a high coefficient of thermal expansion (770×10⁻⁶) Hence, upon heating of poly-silicon layer 5, the PTFE layer 10 will undergo rapid thermal expansion relative to the field oxide layer 3. The rapid thermal expansion of the PTFE layer 10 results in the two layers 10, 3 acting as a thermal actuator, resulting in a bending of the actuator arm 2 in the direction generally indicated 12. The movement is controlled by the amount of current passing through leads 7 and 8 and coil 5.

Turning now to FIG. 2 there is illustrated a single thermal actuator 20 constructed in accordance with another embodiment of the present invention. The thermal actuator 20 includes an electrical circuit comprising leads 26, 27 connecting to a serpentine resistive element 28. The resistive element 28 can comprise a copper layer in this respect, a copper stiffener 29 is provided to provide support for one end of the thermal actuator 20.

The copper resistive element 28 is constructed in a serpentine manner to provide very little tensive strength along the length of the thermal actuator 20. The copper resistive element is embedded in a polytetrafluoroethylene (PTFE) layer 32. The PTFE layer 32 has a very high coefficient of thermal expansion (approximately 770×10⁻⁶). This layer undergoes rapid expansion when heated by the copper heater 28. The copper heater 28 is positioned closer to the top surface of the PTFE layer, thereby heating the upper level of the PTFE layer 32 faster than the bottom level, resulting in a bending down of the thermal actuator 20 towards the bottom of the chamber 24.

Turning now to FIG. 3, there is illustrated an exploded perspective view of a thermal actuator constructed in accordance with one embodiment of the present invention. The basic fabrication steps are:

1) Starting with the single crystal silicon wafer, which has a buried epitaxial layer 36 of silicon which is heavily doped with boron. The boron should be doped to preferably 10²⁰ atoms per cm³ of boron or more and be approximately 3 μm thick. The lightly doped silicon epitaxial layer 35 on top of the boron doped layer should be approximately 8 μm thick, and be doped in a manner suitable for the semi-conductor device technology chosen.

2) On top of the silicon epitaxial layer 35 is fabricated a circuitry layer 37 according to the process chosen, up until the oxide layer over second level matter layers.

3) Next, a silicon nitride passivation layer 38 is deposited.

4) Next, the actuator 20 (FIG. 2) is constructed. The actuator comprises one copper layer 39 embedded in a PTFE layer 40. The copper layer 39 comprises both the heater portion 28 and planar portion 29 (of FIG. 2). Initially, a bottom part of the PTFE layer 40 is deposited, on top of which the copper layer 39 is then deposited. The copper layer 39 is etched to form the heater portion 28 and planar portion 29 (of FIG. 1). Subsequently, the top portion of the PTFE layer 40 is deposited to complete the PTFE layer 40 which is shown as one layer in FIG. 3 for clarity.

5) Etch through the PTFE, and all the way down to silicon in the region around the three sides of the thermal actuator. The etched region should be etched on all previous lithographic steps, so that the etch to silicon does not require strong selectivity against PTFE.

6) Etch the epitaxial silicon layer 35, which stops on (111) crystallographic planes or on heavily boron doped silicon. This etch forms the chamber 4 (FIG. 2).

Thermal actuators such as these illustrated in FIG. 1 and FIG. 2 can be utilised in many different devices in MEMS processes where actuation is required. This can include but is not limited to:

1. The utilisation of actuators in ink jet devices to actuate the ejection of ink.

2. The utilisation of actuation devices for the turbulence control of aircraft wings through the independent monitoring of turbulence and adjustment of wing surface profiles.

3. The utilisation of actuators for micro-mirror arrays devices utilised in image projection systems.

4. The utilisation of actuators in cilia arrays for the fine position adjustment of devices.

5. The utilisation of actuators in optical micro-bench positioning of optical elements.

6. The utilisation of fine optical fibre position control. Utilisation of actuators in micro-pumping.

7. The utilisation of actuators in MEMS devices such as micro-tweezers etc.

Of course, other forms of thermal actuators can just as easily be constructed in accordance with the principles of the preferred embodiment. For example a rotational actuator utilising a serpentine layer and an arcuate PTFE layer could be constructed. A push or buckle actuator could be constructed from a serpentine layer encased in a PTFE layer.

It would be appreciated by a person skilled in the art that numerous variations and/or modifications may be made to the present invention as shown in the specific embodiment without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects to be illustrative and not restrictive.

Ink Jet Technologies

The embodiments of the invention use an ink jet printer type device. Of course many different devices could be used. However presently popular ink jet printing technologies are unlikely to be suitable.

The most significant problem with thermal inkjet is power consumption. This is approximately 100 times that required for high speed, and stems from the energy-inefficient means of drop ejection. This involves the rapid boiling of water to produce a vapor bubble which expels the ink. Water has a very high heat capacity, and must be superheated in thermal inkjet applications. This leads to an efficiency of around 0.02%, from electricity input to drop momentum (and increased surface area) out.

The most significant problem with piezoelectric inkjet is size and cost. Piezoelectric crystals have a very small deflection at reasonable drive voltages, and therefore require a large area for each nozzle. Also, each piezoelectric actuator must be connected to its drive circuit on a separate substrate. This is not a significant problem at the current limit of around 300 nozzles per print head, but is a major impediment to the fabrication of pagewide print heads with 19,200 nozzles.

Ideally, the inkjet technologies used meet the stringent requirements of in-camera digital color printing and other high quality, high speed, low cost printing applications. To meet the requirements of digital photography, new inkjet technologies have been created. The target features include:

low power (less than 10 Watts)

high resolution capability (1,600 dpi or more)

photographic quality output

low manufacturing cost

small size (pagewidth times minimum cross section)

high speed (<2 seconds per page).

All of these features can be met or exceeded by the inkjet systems described below with differing levels of difficulty. 45 different inkjet technologies have been developed by the Assignee to give a wide range of choices for high volume manufacture. These technologies form part of separate applications assigned to the present Assignee as set out in the table below.

The inkjet designs shown here are suitable for a wide range of digital printing systems, from battery powered one-time use digital cameras, through to desktop and network printers, and through to commercial printing systems

For ease of manufacture using standard process equipment, the print head is designed to be a monolithic 0.5 micron CMOS chip with MEMS post processing. For color photographic applications, the print head is 100 mm long, with a width which depends upon the inkjet type. The smallest print head designed is IJ38, which is 0.35 mm wide, giving a chip area of 35 square mm. The print heads each contain 19,200 nozzles plus data and control circuitry.

Ink is supplied to the back of the print head by injection molded plastic ink channels. The molding requires 50 micron features, which can be created using a lithographically micromachined insert in a standard injection molding tool. Ink flows through holes etched through the wafer to the nozzle chambers fabricated on the front surface of the wafer. The print head is connected to the camera circuitry by tape automated bonding.

Cross-Referenced Applications

The following table is a guide to cross-referenced patent applications filed concurrently herewith and discussed hereinafter with the reference being utilized in subsequent tables when referring to a particular case:

    ______________________________________                                         Docket                                                                         No.   Reference                                                                               Title                                                           ______________________________________                                         IJ01US                                                                               IJ01     Radiant Plunger Ink Jet Printer                                 IJ02US                                                                               IJ02     Electrostatic Ink Jet Printer                                   IJ03US                                                                               IJ03     Planar Thermoelastic Bend Actuator Ink Jet                      IJ04US                                                                               IJ04     Stacked Electrostatic Ink Jet Printer                           IJ05US                                                                               IJ05     Reverse Spring Lever Ink Jet Printer                            IJ06US                                                                               IJ06     Paddle Type Ink Jet Printer                                     IJ07US                                                                               IJ07     Permanent Magnet Electromagnetic Ink Jet Printer                IJ08US                                                                               IJ08     Planar Swing Grill Electromagnetic Ink Jet Printer              IJ09US                                                                               IJ09     Pump Action Refill Ink Jet Printer                              IJ10US                                                                               IJ10     Pulsed Magnetic Field Ink Jet Printer                           IJ11US                                                                               IJ11     Two Plate Reverse Firing Electromagnetic Ink Jet                               Printer                                                         IJ12US                                                                               IJ12     Linear Stepper Actuator Ink Jet Printer                         IJ13US                                                                               IJ13     Gear Driven Shutter Ink Jet Printer                             IJ14US                                                                               IJ14     Tapered Magnetic Pole Electromagnetic Ink Jet                                  Printer                                                         IJ15US                                                                               IJ15     Linear Spring Electromagnetic Grill Ink Jet Printer             IJ16US                                                                               IJ16     Lorenz Diaphragm Electromagnetic Ink Jet Printer                IJ17US                                                                               IJ17     PTFE Surface Shooting Shuttered Oscillating                                    Pressure Ink Jet Printer                                        IJ18US                                                                               IJ18     Buckle Grip Oscillating Pressure Ink Jet Printer                IJ19US                                                                               IJ19     Shutter Based Ink Jet Printer                                   IJ20US                                                                               IJ20     Curling Calyx Thermoelastic Ink Jet Printer                     IJ21US                                                                               IJ21     Thermal Actuated Ink Jet Printer                                IJ22US                                                                               IJ22     Iris Motion Ink Jet Printer                                     IJ23US                                                                               IJ23     Direct Firing Thermal Bend Actuator Ink Jet Printer             IJ24US                                                                               IJ24     Conductive PTFE Ben Activator Vented Ink Jet                                   Printer                                                         IJ25US                                                                               IJ25     Magnetostrictive Ink Jet Printer                                IJ26US                                                                               IJ26     Shape Memory Alloy Ink Jet Printer                              IJ27US                                                                               IJ27     Buckle Plate Ink Jet Printer                                    IJ28US                                                                               IJ28     Thermal Elastic Rotary Impeller Ink Jet Printer                 IJ29US                                                                               IJ29     Thermoelastic Bend Actuator Ink Jet Printer                     IJ30US                                                                               IJ30     Thermoelastic Bend Actuator Using PTFE and                                     Corrugated Copper Ink Jet Printer                               IJ31US                                                                               IJ31     Bend Actuator Direct Ink Supply Ink Jet Printer                 IJ32US                                                                               IJ32     A High Young's Modulus Thermoelastic Ink Jet                                   Printer                                                         IJ33US                                                                               IJ33     Thermally actuated slotted chamber wall ink jet                                printer                                                         IJ34US                                                                               IJ34     Ink Jet Printer having a thermal actuator                                      comprising an external coiled spring                            IJ35US                                                                               IJ35     Trough Container Ink Jet Printer                                IJ36US                                                                               IJ36     Dual Chamber Single Vertical Actuator Ink Jet                   IJ37US                                                                               IJ37     Dual Nozzle Single Horizontal Fulcrum Actuator                                 Ink Jet                                                         IJ38US                                                                               IJ38     Dual Nozzle Single Horizontal Actuator Ink Jet                  IJ39US                                                                               IJ39     A single bend actuator cupped paddle ink jet                                   printing device                                                 IJ40US                                                                               IJ40     A thermally actuated ink jet printer having a                                  series of thermal actuator units                                IJ41US                                                                               IJ41     A thermally actuated ink jet printer including                                 a tapered heater element                                        IJ42US                                                                               IJ42     Radial Back-Curling Thermoelastic Ink Jet                       IJ43US                                                                               IJ43     Inverted Radial Back-Curling Thermoelastic Ink Jet              IJ44US                                                                               IJ44     Surface bend actuator vented ink supply ink jet                                printer                                                         IJ45US                                                                               IJ45     Coil Acutuated Magnetic Plate Ink Jet Printer                   ______________________________________                                    

Tables of Drop-on-Demand Inkjets

Eleven important characteristics of the fundamental operation of individual inkjet nozzles have been identified. These characteristics are largely orthogonal, and so can be elucidated as an eleven dimensional matrix. Most of the eleven axes of this matrix include entries developed by the present assignee.

The following tables form the axes of an eleven dimensional table of inkjet types.

Actuator mechanism (18 types)

Basic operation mode (7 types)

Auxiliary mechanism (8 types)

Actuator amplification or modification method (17 types)

Actuator motion (19 types)

Nozzle refill method (4 types)

Method of restricting back-flow through inlet (10 types)

Nozzle clearing method (9 types)

Nozzle plate construction (9 types)

Drop ejection direction (5 types)

Ink type (7 types)

The complete eleven dimensional table represented by these axes contains 36.9 billion possible configurations of inkjet nozzle. While not all of the possible combinations result in a viable inkjet technology, many million configurations are viable. It is clearly impractical to elucidate all of the possible configurations. Instead, certain inkjet types have been investigated in detail. These are designated IJ01 to IJ45 above.

Other inkjet configurations can readily be derived from these 45 examples by substituting alternative configurations along one or more of the 11 axes. Most of the IJ01 to IJ45 examples can be made into inkjet print heads with characteristics superior to any currently available inkjet technology.

Where there are prior art examples known to the inventor, one or more of these examples are listed in the examples column of the tables below. The IJ01 to IJ45 series are also listed in the examples column. In some cases, a printer may be listed more than once in a table, where it shares characteristics with more than one entry.

Suitable applications include: Home printers, Office network printers, Short run digital printers, Commercial print systems, Fabric printers, Pocket printers, Internet WWW printers, Video printers, Medical imaging, Wide format printers, Notebook PC printers, Fax machines, Industrial printing systems, Photocopiers, Photographic minilabs etc.

The information associated with the aforementioned 11 dimensional matrix are set out in the following tables.

       - Description Advantages Disadvantages Examples        ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INK DROPS)        Actuator        Mechanism        Thermal An electrothermal heater heats the ♦ Large force        generated ♦ High power ♦ Canon Bubblejet         bubble ink to above boiling point, ♦       Simple construction ♦ Ink carrier limited to water 1979      Endo et al GB         transferring significant heat to the ♦ No moving parts      ♦       Low efficiency patent 2,007, 162                           aqueous ink.        A bubble nucleates and ♦ Fast operation ♦      High temperatures required ♦       Xerox heater-in-pit             quickly forms, expelling the ink.      ♦ Small chip area required for ♦ High      mechanical stress 1990 Hawkins et al         The efficiency of the process is low, actuator ♦      Unusual materials required USP 4,899,181         with typically less than 0.05% of the  ♦ Large drive      transistors ♦       Hewlett-Packard TIJ                            electrical energy being      transformed  ♦ Cavitation causes actuator failure 1982      Vaught et al         into kinetic energy of the drop.  ♦ Kogation reduces      bubble formation USP 4,490,728           ♦       Large print heads are difficult to                      fabricate             Piezoelectric A piezoelectric crystal such as lead ♦        Low power consumption ♦ Very large area required for      actuator ♦       Kyser et al USP                                   lanthanum zirconate      (PZT) is ♦ Many ink types can be used ♦      Difficult to integrate with electronics 3,946,398         electrically activated, and either ♦ Fast operation      ♦ High voltage drive transistors required ♦      Zoltan USP         expands, shears, or bends to apply ♦ High efficiency      ♦ Full pagewidth print heads impractical 3,683,212                pressure to the ink, ejecting drops. due to actuator size      ♦       1973 Stemme USP                                              .diamond-so       lid.       Requires electrical poling in high field 3,747,120      strengths during manufacture ♦       Epson Stylus                     ♦       Tektronix                   ♦       IJ04                         Electro- An electric field is used to      activate ♦ Low power consumption ♦ Low      maximum strain (approx. 0.01%) ♦ Seiko Epson, Usui et            strictive electrostriction in relaxor materials ♦      Many ink types can be used ♦ Large area required for      actuator due to all JP 253401/96         such as lead lanthanum zirconate ♦       Low thermal expansion low strain ♦       IJ04                     titanate (PLZT) or lead magnesium .diamond-soli       d. Electric field strength ♦ Response speed is marginal      (˜10 μs)         niobate (PMN). required (approx. 3.5 V/μm) ♦ High      voltage drive transistors required          can be generated without ♦ Full pagewidth print heads      impractical          difficulty due to actuator size          ♦       Does not require electrical                             poling        Ferroelectric An electric field is used to induce a ♦      Low power consumption ♦ Difficult to integrate with      electronics ♦       IJ04                                           phase transition between        the ♦ Many ink types can be used ♦ Unusual        materials such as PLZSnT are         antiferroelectric (AFE) and ♦ Fast operation (<1 μs)        required         ferroelectric (FE) phase. Perovskite ♦ Relatively high      longitudinal ♦       Actuators require a large area                materials such as tin      modified lead strain         lanthanum zirconate titanate ♦       High efficiency            (PLZSnT) exhibit large strains of up      ♦       Electric field strength of                                 to 1%      associated with the AFE to FE around 3 V/μm can be         phase transition. readily provided        Electrostatic Conductive plates are separated by a ♦ Low        power consumption ♦ Difficult to operate electrostatic      ♦       IJ02, IJ04                                                plates      compressible or fluid dielectric ♦ Many ink types can be      used devices in an aqueous environment         (usually air). Upon application of a ♦ Fast operation      ♦       The electrostatic actuator will normally                   voltage, the        plates attract each other need to be separated from the ink         and displace ink, causing drop ♦ Very large area      required to achieve         ejection. The conductive plates may high forces         be in a comb or honeycomb ♦       High voltage drive transistors may be         structure, or stacked to increase the required         surface area and therefore the force. ♦ Full pagewidth      print heads are not           competitive due to actuator size        Electrostatic A strong electric field is applied to ♦      Low current consumption ♦       High voltage required ♦       1989 Saito et al, USP              pull on ink the ink, whereupon      electrostatic ♦ Low temperature ♦ May be      damaged by sparks due to air 4,799,068         attraction accelerates the ink towards breakdown ♦ 1989        Miura et al,         the print medium. ♦ Required field strength increases      as the USP 4,810,954           drop size decreases ♦       Tone-jet                            ♦ High voltage drive      transistors required           ♦       Electrostatic field attracts dust                    Permanent An      electromagnet directly attracts a ♦ Low power consumption      ♦ Complex fabrication ♦       IJ07, IJ10            magnet permanent magnet, displacing ink .diamond-s       olid. Many ink types can be used ♦ Permanent magnetic      material such as        electro- and causing drop ejection. Rare earth ♦ Fast      operation Neodymium Iron Boron (NdFeB)        magnetic magnets with a field strength around ♦ High      efficiency required.         1 Tesla can be used. Examples are: ♦ Easy extension      from single ♦       High local currents required                   Samarium Cobalt (SaCo)      and nozzles to pagewidth print ♦ Copper metalization      should be used for         magnetic materials in the heads long electromigration lifetime and      low         neodymium iron boron family resistivity         (NdFeB, NdDyFeBNb, NdDyFeB, ♦ Pigmented inks are      usually infeasible         etc) ♦       Operating temperature limited to the                 Curie temperature      (around 540 K)        Soft magnetic A solenoid induced a magnetic field ♦ Low      power consumption ♦ Complex fabrication ♦      IJ01, IJ05, IJ08, IJ10        core electro- in a soft magnetic core or yoke ♦ Many ink        types can be used ♦ Materials not usually present in a      ♦       IJ12, IJ14, IJ15, IJ17                                    magnetic      fabricated from a ferrous material ♦ Fast operation CMOS      fab such as NiFe, CoNiFe, or         such as electroplated iron alloys such ♦       High efficiency CoFe are required         as CoNiFe [1], CoFe, or NiFe alloys. ♦ Easy extension      from single ♦       High local currents required                   Typically, the soft      magnetic material nozzles to pagewidth print ♦ Copper      metalization should be used for         is in two parts, which are normally heads long electromigration      lifetime and low         held apart by a spring. When the resistivity         solenoid is actuated, the two parts ♦ Electroplating is        required         attract, displacing the ink. ♦ High saturation flux      density is required           (2.0-2.1 T is achievable with CoNiFe           [1])        Magnetic The Lorenz force acting on a current ♦ Low      power consumption ♦ Force acts as a twisting motion      ♦       IJ06, IJ11, IJ13, IJ16                                    Lorenz force      carrying wire in a magnetic field is ♦ Many ink types can      be used ♦       Typically, only a quarter of the                   utilized. .diamond-so       lid.       Fast operation solenoid length provides force in a      This allows the magnetic field to be ♦ High efficiency      useful direction         supplied externally to the print head, ♦ Easy extension        from single ♦       High local currents required                 for example with rare      earth nozzles to pagewidth print ♦ Copper metalization      should be used for         permanent magnets. heads long electromigration lifetime and low              Only the current carrying wire need resistivity         be fabricated on the print-head, ♦ Pigmented inks are      usually infeasible         simplifying materials requirements.        Magneto- The actuator uses the giant ♦ Many ink types      can be used ♦       Force acts as a twisting motion ♦ Fischenbeck, USP              striction magnetostrictive effect of materials ♦      Fast operation ♦ Unusual materials such as Terfenol-D      4,032,929         such as Terfenol-D (an alloy of ♦ Easy extension from      single are required ♦       IJ25                                   terbium, dysprosium and iron      nozzles to pagewidth print ♦ High local currents required         developed at the Naval Ordnance heads ♦       Copper metalization should be used for         Laboratory, hence Ter-Fe-NOL). For ♦ High force is      available long electromigration lifetime and low         best efficiency, the actuator should  resistivity         be pre-stressed to approx. 8 MPa.  ♦ Pre-stressing may      be required        Surface Ink under positive pressure is held in ♦ Low      power consumption ♦ Requires supplementary force to effect        ♦       Silverbrook, EP 0771                                    tension a      nozzle by surface tension. The ♦ Simple construction drop      separation 658 A2 and related        reduction surface tension of the ink is reduced ♦ No      unusual materials ♦ Requires special ink surfactants      patent applications         below the bubble threshold, causing required in fabrication .diamond-s       olid.       Speed may be limited by surfactant                                  the        ink to egress from the nozzle. ♦ High efficiency      properties          ♦       Easy extension from single                              nozzles to      pagewidth print          heads        Viscosity The ink viscosity is locally reduced ♦ Simple      construction ♦ Requires supplementary force to effect      ♦       Silverbrook, EP 0771                                      reduction to      select which drops are to be ♦ No unusual materials drop      separation 658 A2 and related         ejected. A viscosity reduction can be required in fabrication      ♦ Requires special ink viscosity patent applications              achieved electrothermally with most ♦ Easy      extension from single properties         inks, but special inks can be nozzles to pagewidth print .diamond-soli       d.       High speed is difficult to achieve      engineered for a 100: I viscosity heads ♦ Requires      oscillating ink pressure         reduction. ♦       A high temperature difference                  (typically 80 degrees)      is required        Acoustic An acoustic wave is generated and ♦ Can operate        without a ♦ Complex drive circuitry ♦ 1993        Hadimioglu e         focussed upon the drop ejection nozzle plate ♦ Complex      fabrication al, EUP 550,192         region. ♦ Low efficiency ♦ 1993 Elrod et      al, EUP           ♦       Poor control of drop position 572,220                   ♦        Poor control of drop volume        Thermoelastic An actuator which relies upon ♦ Low power      consumption ♦ Efficient aqueous operation requires a      ♦       IJ03, IJ09, IJ17, IJ18                                    bend actuator        differential thermal expansion upon ♦ Many ink types can        be used thermal insulator on the hot side ♦ IJ19, IJ20,      IJ21, IJ22         Joule heating is used. ♦ Simple planar fabrication      ♦ Corrosion prevention can be difficult ♦      IJ23, IJ24, IJ27, IJ28          ♦ Small chip area required for ♦      Pigmented inks may be infeasible, as ♦ IJ29, IJ30, IJ31,      IJ32          each actuator pigment particles may jam the bend ♦      IJ33, IJ34, IJ35, IJ36          ♦ Fast operation actuator ♦ IJ37, IJ38 ,        IJ39, IJ40          ♦ High efficiency ♦       IJ41                    ♦ CMOS compatible voltages                and currents          ♦       Standard MEMS processes                                 can be used             ♦       Easy extension from single                           nozzles to      pagewidth print          heads        High CTE A material with a very high ♦ High force can be        generated ♦ Requires special material (e.g. PTFE)      ♦       IJ09, IJ17, IJ18, IJ20                                    thermoelastic        coefficient of thermal expansion ♦ PTFE is a candidate      for low ♦       Requires a PTFE deposition process, ♦ IJ21, IJ22, IJ23,      IJ24        actuator (CTE) such as dielectric constant which is not yet standard      in ULSI fabs ♦       IJ27, IJ28, IJ29, IJ30                        polytetrafluoroethylene      (PTFE) is insulation in ULSI ♦ PTFE deposition cannot be      followed ♦       IJ31, IJ42, IJ43, IJ44                            used. As high CTE      materials are ♦ Very low power with high temperature      (above 350°       C.)                                                     usually      non-conductive, a heater consumption processing         fabricated from a conductive ♦ Many ink types can be      used ♦       Pigmented inks may be infeasible, as                  material is      incorporated. A 50 μm ♦ Simple planar fabrication      pigment particles may jam the bend         long PTFE bend actuator with ♦ Small chip area required        for actuator         polysilicon heater and 15 mW power each actuator         input can provide 180 μN force and ♦ Fast operation         10 μm deflection. Actuator motions ♦ High efficiency         include: ♦       CMOS compatible voltages                       1) Bend and currents            2) Push ♦       Easy extension from single                   3) Buckle nozzles to      pagewidth print         4) Rotate heads        Conductive A polymer with a high coefficient of ♦ High      force can be generated ♦ Requires special materials      ♦       IJ24                                                      polymer      thermal expansion (such as PTFE) is ♦ Very low power      development (High CTE conductive        thermoelastic doped with conducting substances to consumption polymer)        actuator increase its conductivity to about 3 ♦ Many ink        types can be used ♦ Requires a PTFE deposition process,         orders of magnitude below that of ♦ Simple planar      fabrication which is not yet standard in ULSI fabs         copper. The conducting polymer ♦ Small chip area      required for ♦       PTFE deposition cannot be followed            expands when resistively      heated. each actuator with high temperature (above 350° C.)              Examples of conducting dopants ♦ Fast operation      processing         include: ♦ High efficiency ♦ Evaporation      and CVD deposition         1) Carbon nanotubes . CMOS compatible voltages techniques cannot be      used         2) Metal fibers and currents ♦ Pigmented inks may be      infeasible, as         3) Conductive polymers such as ♦ Easy extension from      single pigment particles may jam the bend         doped polythiophene nozzles to pagewidth print actuator         4) Carbon granules heads        Shape memory A shape memory alloy such as TiNi ♦ High      force is available ♦ Fatigue limits maximum number of      ♦       IJ26                                                      alloy (also      known as Nitinol - Nickel (stresses of hundreds of cycles         Titanium alloy developed at the MPa) ♦ Low strain (1%)      is required to extend         Naval Ordnance Laboratory) is ♦ Large strain is      available fatigue resistance         thermally switched between its weak (more than 3%) ♦      Cycle rate limited by heat removal         martensitic state and its high ♦ High corrosion      resistance ♦       Requires unusual materials (TiNi)               stiffness austenic      state. The shape of ♦ Simple construction ♦      The latent heat of transformation must         the actuator in its martensitic state is ♦ Easy      extension from single be provided         deformed relative to the austenic nozzles to pagewidth print .diamond-       solid.       High current operation      shape. The shape change causes heads ♦       Requires pre-stressing to distort the         ejection of a drop. ♦ Low voltage operation martensitic        state        Linear Linear magnetic actuators include ♦ Linear      Magnetic actuators ♦ Requires unusual semiconductor      ♦       IJ12                                                      Magnetic the      Linear Induction Actuator (LIA), can be constructed with materials such      as soft magnetic alloys        Actuator Linear Permanent Magnet high thrust, long travel, and (e.g.      CoNiFe [1])         Synchronous Actuator (LPMSA), high efficiency using planar .diamond-so       lid.       Some varieties also require permanent      Linear Reluctance Synchronous semiconductor fabrication magnetic      materials such as         Actuator (LRSA), Linear Switched techniques Neodymium iron boron      (NdFeB)         Reluctance Actuator (LSRA), and ♦ Long actuator travel      is ♦       Requires complex multi-phase drive                      the Linear      Stepper Actuator (LSA). available circuitry          ♦ Medium force is available ♦ High      current operation          ♦       Low voltage operation                                 BASIC OPERATION      MODE        Operational        mode        Actuator This is the simplest mode of ♦ Simple operation        ♦       Drop repetition rate is usually limited ♦ Thermal inkjet        directly operation: the actuator directly ♦ No external      fields required to less than 10 KHz. However, this is ♦      Piezoelectric inkjet        pushes ink supplies sufficient kinetic energy to ♦      Satellite drops can be not fundamental to the method, but is .diamond-sol       id.       IJ01, IJ02, IJ03, IJ04      expel the drop. The drop must have a avoided if drop velocity is related        to the refill method normally ♦ IJ05, IJ06, IJ07, IJ09          sufficient velocity to overcome the less than 4 mls used .diamond-sol       id.       IJ11, IJ12, IJ14, IJ1      surface tension. ♦       Can be efficient, depending ♦ All of the drop kinetic      energy must be ♦       IJ20, IJ22, IJ23, IJ24                       upon the actuator used      provided by the actuator ♦       IJ25 IJ26 IJ27, IJ28                ♦ Satellite drops      usually form if drop ♦       IJ29                                    velocity is greater than 4.5      mls ♦       IJ30, IJ31, IJ32                                          .diamond-solid       .       IJ33, IJ34, IJ35, IJ36          ♦       IJ37, IJ38, IJ39, IJ40                                   ♦       IJ41, IJ42, IJ43, IJ44        Proximity The drops to be printed are selected ♦ Very      simple print head ♦ Requires close proximity between the      ♦       Silverbrook, EP 0771                                       by some      manner (e.g. thermally fabrication can be used print head and the print      media or 658 A2 and related         induced surface tension reduction of ♦ The drop      selection means transfer roller patent applications         pressurized ink). Selected drops are does not need to provide the      ♦       May require two print heads printing                       separated      from the ink in the nozzle energy required to separate altemate rows of      the image         by contact with the print medium or the drop from the nozzle .diamond-       solid.       Monolithic color print heads are                                   a      transfer roller.  difficult        Electrostatic The drops to be printed are selected ♦      Very simple print head ♦ Requires very high electrostatic      field ♦       Silverbrook, EP 0771                                pull on ink by some        manner (e.g. thermally fabrication can be used ♦      Electrostatic field for small nozzle 658 A2 and related         induced surface tension reduction of ♦ The drop      selection means sizes is above air breakdown patent applications                pressurized ink). Selected drops are does not need to provide      the ♦ Electrostatic field may attract dust ♦        Tone-Jet         separated from the ink in the nozzle energy required to separate             by a strong electric field. the drop from the nozzle        Magnetic pull The drops to be printed are selected ♦      Very simple print head ♦       Requires magnetic ink ♦       Silverbrook, EP 0771               on ink by some manner (e.g. thermally        fabrication can be used ♦ Ink colors other than black      are difficult 658 A2 and related         induced surface tension reduction of ♦ The drop      selection means ♦ Requires very high magnetic fields      patent applications         pressurized ink). Selected drops are does not need to provide the            separated from the ink in the nozzle energy required to separate          by a strong magnetic field acting on the drop from the nozzle               the magnetic ink.        Shutter The actuator moves a shutter to ♦ High speed      (>50 KHz) ♦ Moving parts are required ♦      IJ13, IJ17, IJ21         block ink flow to the nozzle, The ink operation can be achieved      ♦       Requires ink pressure modulator                            pressure is      pulsed at a multiple of the due to reduced refill time ♦      Friction and wear must be considered         drop ejection frequency. ♦ Drop timing can be very      ♦       Stiction is possible                                        .diamond-sol       id.       accurate      ♦       The actuator energy can be                                  very low          Shuttered grill The actuator moves a shutter to ♦      Actuators with small travel ♦ Moving parts are required      ♦       IJ08, IJ15, IJ18, IJ19                                     block ink      flow through a grill to the can be used ♦ Requires ink      pressure modulator         nozzle. The shutter movement need ♦ Actuators with      small force ♦ Friction and wear must be considered                only be equal to the width of the grill can be used .diamond-so       lid.       Stiction is possible      holes. ♦       High speed (>50 KHz)                                 operation can be      achieved        Pulsed A pulsed magnetic field attracts an ♦ Extremely      low energy ♦       Requires an external pulsed magnetic ♦       IJ10                magnetic pull `ink pusher` at the drop ejection      operation is possible field        on ink pusher frequency. An actuator controls a ♦ No      heat dissipation ♦ Requires special materials for both the         catch, which prevents the ink pusher problems actuator and the ink      pusher         from moving when a drop is not to  ♦       Complex construction         be ejected.        AUXILIARY MECHANISM (APPLIED TO ALL NOZZLES)        Auxiliary        Mechanism        None The actuator directly fires the ink ♦ Simplicity of        construction ♦ Drop ejection energy must be supplied      ♦       Most inkjets,                                              drop, and      there is no external field or ♦ Simplicity of operation by        individual nozzle actuator including         other mechanism required. ♦ Small physical size      piezoelectric and            the#thermal bubble            ♦       IJ01-IJ07, IJ09, IJ11                                   ♦        IJ12, IJ14, IJ20, IJ22            ♦       IJ23-IJ45                                           Oscillating ink The        ink pressure oscillates, ♦ Oscillating ink pressure can      ♦ Requires external ink pressure ♦       Silverbrook, EP 0771        pressure providing much of the drop ejection provide a refill pulse,      oscillator 658 A2 and related        (including energy. The actuator selects which allowing higher operating        ♦       Ink pressure phase and amplitude must patent applications        acoustic drops are to be fired by selectively speed be carefully      controlled ♦       IJ08, IJ13, IJ15, IJ17                         stimulation) blocking or        enabling nozzles. The ♦ The actuators may operate      ♦ Acoustic reflections in the ink chamber ♦      IJ18, IJ19, IJ21         ink pressure oscillation may be with much lower energy must be      designed for         achieved by vibrating the print head, ♦ Acoustic lenses        can be used         or preferably by an actuator in the to focus the sound on the                ink supply. nozzles        Media The print head is placed in close ♦ Low power      ♦ Precision assembly required ♦ Silverbrook,        EP 0771        proximity proximity to the print medium. ♦ High accuracy        ♦ Paper fibers may cause problems 658 A2 and related            Selected drops protrude from the ♦ Simple print head        ♦ Cannot print on rough substrates patent applications          print head further than unselected construction         drops, and contact the print medium.         The drop soaks into the medium fast         enough to cause drop separation.        Transfer roller Drops are printed to a transfer roller ♦        High accuracy ♦ Bulky ♦ Silverbrook, EP      0771         instead of straight to the print ♦ Wide range of print      ♦       Expensive 658 A2 and related                               medium. A      transfer roller can,also be substrates can be used ♦      Complex construction patent applications         used for proximity drop separation. ♦ Ink can be dried      on the ♦       Tektronix hot melt                                   transfer roller      piezoelectric inkjet            ♦       Any of the IJ series                                Electrostatic An      electric field is used to accelerate ♦       Low power ♦ Field strength required for separation      ♦       Silverbrook, EP 0771                                       selected      drops towards the print ♦ Simple print head of small drops        is near or above air 658 A2 and related         medium. construction breakdown patent applications            ♦       Tone-Jet                                            Direct A magnetic      field is used to accelerate ♦ Low power ♦      Requires magnetic ink ♦       Silverbrook, EP 0771                magnetic field selected drops of      magnetic ink ♦ Simple print head ♦ Requires      strong magnetic field 658 A2 and related         towards the print medium. construction patent applications        Cross The print head is placed in a constant ♦ Does not      require magnetic ♦       Requires external magnet ♦       IJ06, IJ16                      magnetic field magnetic field. The      Lorenz force in a materials to be integrated in ♦ Current      densities may be high,         current carrying wire is used to move the print head resulting in      electromigration problems         the actuator. manufacturing process        Pulsed A pulsed magnetic field is used to ♦ Very low      power operation ♦       Complex print head construction ♦       IJ10                     magnetic field cyclically attract a paddle,      which is possible ♦ Magnetic materials required in print          pushes on the ink. A small actuator ♦ Small print head        size head         moves a catch, which selectively         prevents the paddle from moving.        ACTUATOR AMPLIFICATION OR MODIFICATION METHOD        Actuator        amplification        None No actuator mechanical ♦ Operational simplicity      ♦ Many actuator mechanisms have ♦ Thermal      Bubble         amplification is used. The actuator insufficient travel, or insufficie       nt force, Inkjet         directly drives the drop ejection to efficiently drive the drop      ejection ♦       IJ01, IJ02, IJ06, IJ07                            process. process      ♦       IJ16, IJ25, IJ26                                          Differential      An actuator material expands more ♦ Provides greater      travel in a ♦ High stresses are involved ♦      Piezoelectric        expansion on one side than on the other. The reduced print head area      ♦ Care must be taken that the materials ♦      IJ03, IJ09, IJ17-IJ24        bend actuator expansion may be thermal, ♦ The bend      actuator converts do not delaminate ♦ IJ27, IJ29-IJ39,      IJ42,         piezoelectric, magnetostrictive, or a high force low travel .diamond-s       olid. Residual bend resulting from high ♦ IJ43, IJ44             other mechanism. actuator inechanism to high temperature or high      stress during          travel, lower force formation          mechanism.        Transient bend A trilayer bend actuator where the ♦ Very        good temperature ♦       High stresses are involved ♦       IJ40, IJ41                    actuator two outside layers are identical.        This stability ♦ Care must be taken that the materials          cancels bend due to ambient ♦ High speed, as a new      drop do not delaminate         temperature and residual stress. The can be fired before heat                actuator only responds to transient dissipates         heating of one side or the other. ♦ Cancels residual      stress of          formation        Actuator stack A series of thin actuators are stacked. ♦        Increased travel ♦ Increased fabrication complexity      ♦       Some piezoelectric                                         This can be      appropriate where ♦ Reduced drive voltage ♦      Increased possibility of short circuits ink jets         actuators require high electric field due to pinholes ♦        IJ04         strength, such as electrostatic and         piezoelectric actuators.        Multiple Multiple smaller actuators are used ♦ Increases        the force available ♦ Actuator forces may not add      linearly, ♦       IJ12, IJ13, IJ18, IJ20                          actuators simultaneously        to move the ink. from an actuator reducing efficiency ♦      IJ22, IJ28, IJ42, IJ43         Each actuator need provide only a ♦ Multiple actuators      can be         portion of the force required. positioned to control ink           flow accurately        Linear Spring A linear spring is used to transform a ♦      Matches low travel actuator ♦ Requires print head area for        the spring ♦       IJ15                                          motion with small travel      and high with higher travel         force into a longer travel, lower force requirements         motion. ♦       Non-contact method of                            motion transformation        Reverse spring The actuator loads a spring. When ♦      Better coupling to the ink ♦ Fabrication complexity      ♦       IJ05, IJ11                                                 the actuator        is turned off, the spring ♦ High stress in the spring           releases. This can reverse the         force/distance curve of the actuator         to make it compatible with the         force/time requirements of the drop         ejection.        Coiled A bend actuator is coiled to provide ♦ Increases      travel ♦ Generally restricted to planar ♦      IJ17, IJ21, IJ34, IJ35        actuator greater travel in a reduced chip area. ♦      Reduces chip area implementations due to extreme          ♦ Planar implementations are fabrication difficulty in        other          relatively easy to fabricate. orientations.        Flexure bend A bend actuator has a small region ♦ Simple        means of increasing ♦ Care must be taken not to exceed      the ♦       IJ10, IJ19, IJ33                                      actuator near the        fixture point, which flexes travel of a bend actuator elastic limit in        the flexure area         much more readily than the ♦ Stress distribution is      very uneven         remainder of the actuator. The ♦       Difficult to accurately model with         actuator flexing is effectively finite element analysis         converted from an even coiling to an         angular bend, resulting in greater         travel of the actuator tip.        Gears Gears can be used to increase travel ♦ Low force,      low travel ♦ Moving parts are required ♦      IJ13         at the expense of duration. Circular actuators can be used .diamond-so       lid.       Several actuator cycles are required      gears, rack and pinion, ratchets, and ♦ Can be fabricated      using ♦       More complex drive electronics                       other gearing      methods can be used. standard surface MEMS ♦ Complex      construction          processes ♦ Friction, friction, and wear are possible        Catch The actuator controls a small catch. ♦ Very low      actuator energy ♦ Complex construction ♦      IJ10         The catch either enables or disables ♦ Very small      actuator size ♦       Requires external force                      movement of an ink pusher      that is  ♦       Unsuitable for pigmented inks                     controlled in a bulk      manner.        Buckle plate A buckle plate can be used to change ♦ Very        fast movement ♦ Must stay within elastic limits of the      ♦       S. Hirata et al, "An                                       a slow      actuator into a fast motion. It achievable materials for long device      life Ink-jet Head . . .",         can also convert a high force, low  ♦ High stresses      involved Proc. IEEE MEMS,         travel actuator into a high travel,  ♦ Generally high      power requirement Feb. 1996, pp 418-         medium force motion. ♦       4U2138, IJ27                      Tapered A tapered magnetic pole can      increase ♦ Linearizes the magnetic ♦ Complex        construction ♦       IJ14                                       magnetic pole travel at the      expense of force. force/distance curve        Lever A lever and fulcrum is used to ♦ Matches low      travel actuator ♦       High stress around the fulcrum ♦ IJ32, IJ36, IJ37                transform a motion with small travel with higher travel               and high force into a motion with requirements         longer travel and lower force. The ♦ Fulcrum area has      no linear         lever can also reverse the direction of movement, and can be used            travel. for a fluid seal        Rotary The actuator is connected to a rotary ♦ High      mechanical advantage ♦       Complex construction ♦       IJ28                                impeller impeller. A small angular      deflection ♦ The ratio of force to travel ♦      Unsuitable for pigmented inks         of the actuator results in a rotation of of the actuator can be              the impeller vanes, which push the matched to the nozzle                ink against stationary vanes and out requirements by varying      the         of the nozzle. number of impeller vanes        Acoustic lens A refractive or diffractive (e.g. zone ♦      No moving parts ♦ Large area required ♦ 1993        Hadimioglu et         plate) acoustic lens is used to  ♦ Only relevant for      acoustic ink jets al, EUP 550,192         concentrate sound waves.   ♦ 1993 Elrod et al, EUP                572,220        Sharp A sharp point is used to concentrate ♦ Simple      construction ♦ Difficult to fabricate using standard      ♦       Tone-jet                                                  conductive an        electrostatic field.  VLSI processes for a surface ejecting        point ink-jet           ♦       Only relevant for electrostatic ink jets             ACTUATOR MOTION          Actuator        motion        Volume The volume of the actuator changes, ♦ Simple      construction in the ♦ High energy is typically required to        ♦       Hewlett-Packard                                         expansion      pushing the ink in all directions. case of thermal ink jet achieve      volume expansion. This leads Thermal Inkjet           to thermal stress, cavitation, and ♦ Canon Bubblejet           kogation in thermal inkjet           implementations        Linear, normal The actuator moves in a direction ♦      Efficient coupling to ink High fabrication complexity may be .diamond-sol       id.       IJ01, IJ02, IJ04, IJ07                                               to        chip surface normal to the print head surface. The drops ejected      normal to the required to achieve perpendicular ♦ IJ11,      IJ14         nozzle is typically in the line of surface motion         movement.        Linear, parallel The actuator moves parallel to the ♦      Suitable for planar ♦       Fabrication complexity ♦       IJ12, IJ13, IJ15, IJ33,           to chip surface print head surface.      Drop ejection fabrication ♦ Friction ♦ IJ34,        IJ35, IJ36         may still be normal to the surface.  ♦ Stiction               Membrane An actuator with a high force but ♦ The      effective area of the ♦       Fabrication complexity ♦       1982 Howkins USP                  push small area is used to push a      stiff actuator becomes the ♦ Actuator size 4,459,601              membrane that is in contact with the membrane area .diamond-solid       .       Difficulty of integration in a VLSI        ink.  process        Rotary The actuator causes the rotation of ♦ Rotary      levers may be used ♦ Device complexity ♦      IJ05, IJ08, IJ13, IJ28         some element, such a grill or to increase travel ♦ May      have friction at a pivot point         impeller ♦       Small chip area                                 requirements        Bend The actuator bends when energized. ♦ A very small      change in ♦       Requires the actuator to be made from ♦ 1970 Kyser et al      USP         This may be due to differential dimensions can be at least two      distinct layers, or to have a 3,946,398         thermal expansion, piezoelectric converted to a large motion. thermal        difference across the actuator ♦ 1973 Stemme USP                expansion, magnetostriction, or other   3,747, 120         form of relative dimensional change.   ♦ IJ03, IJ09,      IJ10, IJ19            ♦       IJ23, IJ24, IJ25, IJ29                                  ♦        IJ30, IJ31, IJ33, IJ34            ♦       IJ35                                                Swivel The actuator        swivels around a central ♦ Allows operation where the      ♦ Inefficient coupling to the ink motion ♦      IJ06         pivot. This motion is suitable where net linear force on the         there are opposite forces applied to paddle is zero         opposite sides of the paddle, e.g. ♦ Small chip area           Lorenz force. requirements        Straighten The actuator is normally bent, and ♦ Can be      used with shape ♦ Requires careful balance of stresses to      ♦       IJ26, IJ32                                                 straightens      when energized. memory alloys where the ensure that the quiescent bend      is          austenic phase is planar accurate        Double bend The actuator bends in one direction ♦ One      actuator can be used to ♦ Difficult to make the drops      ejected by ♦       IJ36, IJ37, IJ38                                when one element is      energized, and power two nozzles. both bend directions identical.               bends the other way when another ♦ Reduced chip      size. ♦       A small efficiency loss compared to                  element is      energized. ♦ Not sensitive to ambient equivalent single      bend actuators.          temperature        Shear Energizing the actuator causes a ♦ Can increase      the effective ♦ Not readily applicable to other actuator      ♦       1985 Fishbeck USP                                          shear motion        in the actuator material. travel of piezoelectric mechanisms 4,584,590          actuators        Radial The actuator squeezes an ink ♦ Relatively easy to        fabricate ♦ High force required ♦ 1970      Zoltan USP        constriction reservoir, forcing ink from a single nozzles from glass      ♦       Inefficient 3,683,2 I 2                                    constricted      nozzle. tubing as macroscopic ♦ Difficult to integrate      with VLSI          structures processes        Coil/uncoil A coiled actuator uncoils or coils ♦ Easy to        fabricate as a planar ♦ Difficult to fabricate for      non-planar ♦       IJ17, IJ21, IJ34, IJ35                          more tightly. The      motion of the free VLSI process devices         end of the actuator ejects the ink. ♦ Small area      required, ♦       Poor out-of-plane stiffness                       therefore low cost          Bow The actuator bows (or buckles) in the ♦ Can      increase the speed of ♦ Maximum travel is constrained      ♦       IJ16, IJ18, IJ27                                           middle when      energized. travel ♦       High force required                       ♦ Mechanically      rigid        Push-Pull Two actuators control a shutter. One ♦ The      structure is pinned at ♦ Not readily suitable for inkjets      which ♦       IJ18                                                 actuator pulls the        shutter, and the both ends, so has a high directly push the ink               other pushes it. out-of-plane rigidity        Curl inwards A set of actuators curl inwards to ♦ Good      fluid flow to the ♦ Design complexity ♦      IJ20, IJ42         reduce the volume of ink that they region behind the actuator                enclose. increases efficiency        Curl outwards A set of actuators curl outwards, ♦      Relatively simple ♦       Relatively large chip area ♦       IJ43                           pressurizing ink in a chamber constructio       n         surrounding the actuators, and         expelling ink from a nozzle in the         chamber        Iris Multiple vanes enclose a volume of ♦       High efficiency ♦       High fabrication complexity ♦       IJ22                          ink. These simultaneously rotate,      ♦ Small chip area ♦ Not suitable for      pigmented inks         reducing the volume between the         vanes.        Acoustic The actuator vibrates at a high ♦ The actuator      can be ♦ Large area required for efficient ♦        1993 Hadimioglu et        vibration frequency. physically distant from the operation at useful      frequencies al, EUP 550,192          ink ♦ Acoustic coupling and crosstalk ♦      1993 Elrod et al, EUP           ♦       Complex drive circuitry 572,220                         ♦        Poor control of drop volume and           position        None In various ink jet designs the actuator ♦ No moving        parts ♦       Various other tradeoffs are required to ♦ Silverbrook, EP        0771         does not move.  eliminate moving parts 658 A2 and related            patent applications            ♦       Tone-jet                                            NOZZLE REFILL      METHOD        Nozzle refill        method        Surface After the actuator is energized, it ♦       Fabrication simplicity ♦ Low speed ♦      Thermal inkjet        tension typically returns rapidly to its normal ♦      Operational simplicity ♦ Surface tension force relatively      small ♦       Piezoelectric inkjet                                 position. This      rapid return sucks in  compared to actuator force ♦      IJ01-1107, IJ10-IJ14         air through the nozzle opening. The  ♦ Long refill time        usually dominates the ♦       IJ16, IJ20, IJ22-IJ45              ink surface tension at the nozzle      then  total repetition rate         exerts a small force restoring the         meniscus to a minimum area.        Shuttered Ink to the nozzle chamber is ♦ High speed      ♦ Requires common ink pressure ♦ IJ08, IJ13,        IJ15, IJ17        oscillating ink provided at a pressure that oscillates ♦        Low actuator energy, as the oscillator ♦ IJ18, IJ19,      IJ21        pressure at twice the drop ejection frequency. actuator need only open        or ♦       May not be suitable for pigmented inks                When a drop is to        be ejected, the close the shutter, instead of         shutter is opened for 3 half cycles: ejecting the ink drop         drop ejection, actuator return, and         refill.        Refill actuator After the main actuator has ejected a ♦      High speed, as the nozzle is ♦ Requires two independent      actuators per ♦       IJ09                                         drop a second (refill)      actuator is actively refilled nozzle         energized. The refill actuator pushes         ink into the nozzle chamber. The         refill actuator returns slowly, to         prevent its return from emptying the         chamber again        Positive ink The ink is held a slight positive ♦ High      refill rate, therefore a ♦ Surface spill must be prevented        ♦       Silverbrook, EP 0771                                    pressure      pressure. After the ink drop is high drop repetition rate is .diamond-sol       id.       Highly hydrophobic print head 658 A2 and related      ejected, the nozzle chamber fills possible surfaces are required patent      applications         quickly as surface tension and ink   ♦ Alternative for:         pressure both operate to refill the   ♦ IJ01-IJ07,      IJ10-IJ14         nozzle.   ♦       IJ16, IJ20, IJ22-IJ45                        METHOD OF RESTRICTING      BACK-FLOW THROUGH INLET        Inlet back-flow        restriction        method        Long inlet The ink inlet channel to the nozzle ♦ Design      simplicity ♦ Restricts refill rate ♦ Thermal        inkjet        channel chamber is made long and relatively ♦       Operational simplicity ♦ May result in a relatively large        chip ♦       Piezoelectric inkjet                                narrow, relying on      viscous drag to ♦       Reduces crosstalk area                     reduce inlet back-flow.      ♦       Only partiality effective                                 Positive ink      The ink is under a positive pressure, ♦ Drop selection and        ♦ Requires a method (such as a nozzle ♦      Silverbrook, EP 0771        pressure so that in the quiescent state some of separation forces can      be rim or effective hydrophobizing, or 658 A2 and related         the ink drop already protrudes from reduced both) to prevent flooding        of the patent applications         the nozzle. ♦ Fast refill time ejection surface of the      print head. ♦       Possible operation of                          This reduces the      pressure in the   the following:         nozzle chamber which is required to   ♦ IJ01-IJ07,      IJ09-IJ12         eject a certain volume of ink. The   ♦ IJ14, IJ16,      IJ20, IJ22,         reduction in chamber pressure results   ♦ IJ23-IJ34,      IJ36-IJ41         in a reduction in ink pushed out   ♦       IJ44                 through the inlet.        Baffle One or more baffles are placed in the ♦ The      refill rate is not as ♦ Design complexity ♦      HP Thermal Ink Jet         inlet ink flow. When the actuator is restricted as the long inlet      ♦ May increase fabrication complexity ♦      Tektronix         energized, the rapid ink movement method. (e.g. Tektronix hot melt      Piezoelectric piezoelectric ink jet         creates eddies which restrict the flow ♦ Reduces      crosstalk print heads).         through the inlet. The slower refill         process is unrestricted, and does not         result in eddies.        Flexible flap In this method recently disclosed by ♦      Significantly reduces back- ♦ Not applicable to most      inkjet ♦       Canon                                              restricts inlet      Canon, the expanding actuator flow for edge-shooter configurations              (bubble) pushes on a flexible flap thermal ink jet devices      ♦       Increased fabrication complexity                           that      restricts the inlet.  ♦ Inelastic deformation of polymer      flap           results in creep over extended use        Inlet filter A filter is located between the ink ♦      Additional advantage of ink ♦ Restricts refill rate      ♦       IJ04, IJ12, IJ24, IJ27                                     inlet and      the nozzle chamber. The filtration ♦ May result in complex        construction ♦       IJ29, IJ30                                  filter has a multitude of      small holes ♦       Ink filter may be fabricated                   or slots, restricting      ink flow. The with no additional process         filter also removes particles which steps         may block the nozzle.        Small inlet The ink inlet channel to the nozzle ♦ Design        simplicity ♦ Restricts refill rate ♦ IJ02,        IJ37, IJ44        compared to chamber has a substantially smaller  ♦ May      result in a relatively large chip        nozzle cross section than that of the nozzle,  area         resulting in easier ink egress out of  ♦ Only partially        effective         the nozzle than out of the inlet.        Inlet shutter A secondary actuator controls the ♦      Increases speed of the ink- ♦ Requires separate refill      actuator and ♦       IJ09                                          position of a shutter,      closing off the jet print head operation drive circuit         ink inlet when the main actuator is         energized.        The inlet is The method avoids the problem of ♦       Back-flow problem is ♦ Requires careful design to      minimize ♦       IJ01, IJ03, IJ05, IJ06                           located behind inlet      back-flow by arranging the ink- eliminated the negative pressure behind      the paddie ♦       IJ07, IJ10, IJ11, IJ14                         the ink- pushing surface        of the actuator   ♦       IJ16, IJ22, IJ23, IJ25                pushing between the inkjet and      the nozzle.   ♦       IJ28, IJ31, IJ32, IJ33                      surface    ♦      IJ34, IJ35, IJ36, IJ39            ♦       IJ40, IJ41                                          Part of the The      actuator and a wall of the ink ♦ Significant reductions in        ♦ Small increase in fabrication ♦ IJ07,      IJ20, IJ26, IJ31        actuator chamber are arranged so that the back-flow can be achieved      complexity        moves to shut motion of the actuator closes off the ♦      Compact designs possible        off the inlet inlet.        Nozzle In some configurations of ink jet, ♦       Ink back-flow problem is ♦ None related to ink back-flow      on ♦       Silverbrook, EP 0771                                   actuator does      there is no expansion or movement eliminated actuation 658 A2 and      related        not result in of an actuator which may cause ink   patent applications        ink back-flow back-flow through the inlet.   ♦ Valve-jet            ♦       Tone-jet                                                ♦        IJ08,IJ13,IJ15,IJ17            ♦       IJ18,IJ19,IJ21                                      NOZZLE CLEARING      METHOD        Nozzle        Clearing        method        Normal nozzle All of the nozzles are fired ♦ No added      complexity on the ♦ May not be sufficient to displace      dried ♦       Most ink jet systems                                firing periodically,        before the ink has a print head ink ♦ IJ01-IJ07,      IJ09-IJ12         chance to dry. When not in use the   ♦ IJ14, IJ16,      IJ20, IJ22         nozzles are sealed (capped) against   ♦ IJ23-IJ34,      IJ36-IJ45         air.         The nozzle firing is usually         performed during a special clearing         cycle, after first moving the print         head to a cleaning station.        Extra power to In systems which heat the ink, but do ♦      Can be highly effective if ♦ Requires higher drive voltage        for ♦       Silverbrook, EP 0771                                ink heater not boil        it under normal situations, the heater is adjacent to the clearing 658        A2 and related         nozzle clearing can be achieved by nozzle ♦ May require        larger drive transistors patent applications         over-powering the heater and boiling         ink at the nozzle.        Rapid The actuator is fired in rapid ♦ Does not require      extra drive ♦       Effectiveness depends substantially ♦ May be used with          succession of succession. In some configurations, circuits on the      print head upon the configuration of the inkjet ♦       IJ01-IJ07, IJ09-IJ11        actuator this may cause heat build-up at the ♦ Can be      readily controlled nozzle ♦ IJ14, IJ16, IJ20, IJ22               pulses nozzle which boils the ink, clearing and initiated by      digital logic  ♦       IJ23-IJ25, IJ36-IJ45                        the nozzle. In other      situations, it may   ♦       IJ36-IJ45                             cause sufficient vibrations to           dislodge clogged nozzles.        Extra power to Where an actuator is not normally ♦ A      simple solution where ♦ Not suitable where there is a hard        limit ♦       May be used with:                                 ink pushing driven to        the limit of its motion, applicable to actuator movement .diamond-solid       .       IJ03, IJ09, IJ16, IJ20      actuator nozzle clearing may be assisted by   ♦ IJ23,      IJ24, IJ25, IJ27         providing an enhanced drive signal   ♦ IJ29, IJ30,      IJ31, IJ32         to the actuator.   ♦       IJ39, IJ40, IJ41, IJ42                  ♦ IJ43, IJ44,      IJ45        Acoustic An ultrasonic wave is applied to the ♦ A high      nozzle clearing ♦ High implementation cost if system      ♦       IJ08, IJ13, IJ15, IJ17                                    resonance ink        chamber. This wave is of an capability can be achieved does not      already include an acoustic ♦       IJ18, IJ19, IJ21               appropriate amplitude and frequency      ♦       May be implemented at actuator                             to cause      sufficient force at the nozzle very low cost in systems         to clear blockages. This is easiest to which already include         achieve if the ultrasonic wave is at a acoustic actuators         resonant frequency of the ink cavity.        Nozzle A microfabricated plate is pushed ♦ Can clear      severely clogged ♦ Accurate mechanical alignment is      ♦       Silverbrook, EP 0771                                      clearing      plate against the nozzles. The plate has a nozzles required 658 A2 and      related         post for every nozzle. The array of  ♦ Moving parts are        required patent applications         posts  ♦ There is risk of damage to the nozzles                  ♦       Accurate fabrication is required              Ink pressure The pressure        of the ink is ♦ May be effective where ♦      Requires pressure pump or other ♦ May be used with all           pulse temporarily increased so that ink other methods cannot be      pressure actuator IJ series ink jets         streams from all of the nozzles. This used ♦ Expensive         may be used in conjunction with  ♦ Wasteful of ink             actuator energizing.        Print head A flexible `blade` is wiped across the ♦      Effective for planar print ♦ Difficult to use if print      head surface is ♦       Many ink jet systems                      wiper print head surface. The        blade is head surfaces non-planar or very fragile         usually fabricated from a flexible ♦       Low cost ♦       Requires mechanical parts                        polymer, e.g. rubber      or synthetic  ♦       Blade can wear out in high volume            elastomer.  print systems        Separate ink A separate heater is provided at the ♦ Can      be effective where ♦       Fabrication complexity ♦       Can be used with                  boiling heater nozzle although the      normal drop e- other nozzle clearing  many IJ series ink         section mechanism does not require it. methods cannot be used  jets          The heaters do not require individual ♦ Can be      implemented at no         drive circuits, as many nozzles can additional cost in some         be cleared simultaneously, and no inkjet configurations         imaging is required.        NOZZLE PLATE CONSTRUCTION        Nozzle plate        construction        Electroformed A nozzle plate is separately ♦ Fabrication        simplicity ♦ High temperatures and pressures are      ♦       Hewlett Packard                                           nickel      fabricated from electroformed nickel,  required to bond nozzle plate      Thermal Inkjet         and bonded to the print head chip.  ♦ Minimum thickness        constraints           ♦       Differential thermal expansion                       Laser ablated      Individual nozzle holes are ablated ♦ No masks required      ♦ Each hole must be individually formed ♦      Canon Bubblejet        or drilled by an intense UV laser in a nozzle ♦ Can be      quite fast ♦ Special equipment required ♦      1988 Sercel et al.,        polymer plate, which is typically a polymer ♦ Some      control over nozzle ♦ Slow where there are many thousands      SPIE, Vol. 998         such as polyimide or polysulphone profile is possible of nozzles per      print head Excimer Beam          ♦ Equipment required is ♦ May produce      thin burrs at exit holes Applications, pp. 76-          relatively low cost  83            ♦       1993 Watanabe et al.,                                   USP 5,208,604         Silicon micro- A separate nozzle plate is ♦ High      accuracy is attainable ♦       Two part construction ♦       K. Bean, IEEE                      machined micromachined from single      crystal  ♦       High cost Transactions on                         silicon, and bonded      to the print head  ♦ Requires precision alignment Electron        Devices,         wafer.  ♦ Nozzles may be clogged by adhesive Vol.      ED-25, No. 10,           1978 pp 1185-1195            ♦       Xerox 1990 Hawkin                                       et al., USP      4,899,181        Glass Fine glass capillaries are drawn from ♦ No      expensive equipment ♦       Very small nozzle sizes are difficult to ♦ 1970 Zoltan      USP        capillaries glass tubing. This method has been required form 3,683,212         used for making individual nozzles, ♦ Simple to make      single ♦       Not suited for mass production                      but is difficult to        use for bulk nozzles         manufacturing of print heads with         thousands of nozzles.        surface micro- layer using standard VLSI deposition ♦      Monolithic nozzle plate to form the nozzle 658 A2 and related        machined techniques. Nozzles are etched in the ♦ Low      cost chamber patent applications        using VLSI nozzle plate using VLSI lithography ♦      Existing processes can be ♦ Surface may be fragile to the      touch ♦       IJ01, IJ02, IJ04, IJ11                              lithographic and      etching. used  ♦       IJ12, IJ17, IJ18, IJ20                     processes    ♦        IJ22, IJ24, IJ27, IJ28            ♦       IJ29, IJ30, IJ31, IJ32                                  ♦        IJ33, IJ34, IJ36, IJ37            ♦       IJ38, IJ39, IJ40, IJ41                                  ♦        IJ42, IJ43, IJ44        Monolithic, The nozzle plate is a buried etch stop ♦      High accuracy (<1 μm) ♦ Requires long etch times      ♦       IJ03, IJ05, IJ06, IJ07                                    etched in the        wafer. Nozzle chambers are ♦ Monolithic ♦      Requires a support wafer ♦       IJ08, IJ09, IJ10, IJ13           through etched in the front of the      wafer, and ♦ Low cost  ♦ IJ14, IJ15, IJ16,      IJ19        substrate the wafer is thinned from the back ♦ No      differential expansion  ♦       IJ21, IJ23, IJ25, IJ26             side. Nozzles are then etched in the         etch stop layer.        No nozzle Various methods have been tried to ♦ No      nozzles to become ♦ Difficult to control drop position      ♦       Ricoh 1995 Sekiya et                                      plate      eliminate the nozzles entirely, to clogged accurately al USP 5,412,413          prevent nozzle clogging. These  ♦ Crosstalk problems      ♦       1993 Hadimioglu et                                         include      thermal bubble mechanisms   al EUP 550,192         and acoustic lens mechanisms   ♦ 1993 Elrod et al EUP             572,220        Trough Each drop ejector has a trough ♦       Reduced manufacturing ♦       Drop firing direction is sensitive to ♦       IJ35                through which a paddle moves. complexity wicking.          There is no nozzle plate. ♦       Monolithic                  Nozzle slit The elimination of nozzle holes        and ♦ No nozzles to become ♦ Difficult to      control drop position ♦       1989 Saito et al USP                instead of replacement by a slit      encompassing clogged accurately 4,799,068        individual many actuator positions reduces  ♦ Crosstalk      problems        nozzles nozzle clogging, but increases         crosstalk due to ink surface waves        DROP EJECTION DIRECTION        Ejection        direction        Edge Ink flow is along the surface of the ♦ Simple      construction ♦ Nozzles limited to edge ♦      Canon Bubblejet        (`edge chip, and ink drops are ejected from ♦ No silicon        etching required ♦ High resolution is difficult 1979      Endo et al GB        shooter`) the chip edge. ♦ Good heat sinking via      ♦ Fast color printing requires one print patent 2,007,162          substrate head per color ♦ Xerox heater-in-pit                 ♦ Mechanically strong  1990 Hawkins et al               ♦       Ease of chip handing  USP 4,899,181                  ♦      Tone-jet        Surface Ink flow is along the surface of the ♦ No bulk      silicon etching ♦       Maximum ink flow is severely ♦ Hewlett-Packard TIJ              (`roof shooter`) chip, and ink drops are ejected from required      restricted 1982 Vaught et al         the chip surface, normal to the plane ♦ Silicon can      make an  USP 4,490,728         of the chip. effective heat sink  ♦ IJ02,IJ11,IJ12,IJ20          ♦ Mechanical strength  ♦       IJ22             Through chip, Ink flow is through the chip, and ink      ♦ High ink flow ♦ Requires bulk silicon      etching ♦       Silverbrook, EP 0771                              forward drops are      ejected from the front ♦ Suitable for pagewidth print  658        A2 and related        (`up shooter`) surface of the chip. ♦ High nozzle      packing  patent applications          density therefore low  ♦ IJ04, IJ17, IJ18, IJ24                manufacturing cost  ♦       IJ27-IJ45                   Through chip, Ink flow is through the chip,        and ink ♦ High ink flow ♦ Requires wafer      thinning ♦       IJ01, IJ03, IJ05,                                reverse drops are      ejected from the rear ♦ Suitable for pagewidth print      ♦ Requires special handling during ♦ IJ07,      IJ08, IJ09, IJ10        (`down surface of the chip. ♦ High nozzle packing      manufacture ♦       IJ13, IJ14, IJ15, IJ16                        shooter`) density      therefore low  ♦       IJ19, IJ21, IJ23, IJ25                       manufacturing cost      ♦       IJ26                                                      Through Ink      flow is through the actuator, ♦ Suitable for piezoelectric        ♦ Pagewidth print heads require several ♦      Epson Stylus        actuator which is not fabricated as part of the print heads thousand      connections to drive circuits ♦ Tektronix hot melt                same substrate as the drive  ♦ Cannot be      manufactured in standard piezoelectric ink jets         transistors.  CMOS fabs           ♦       Complex assembly required                            INKTYPE        Ink type        Aqueous, dye Water based ink which typically ♦       Environmentally friendly ♦ Slow drying ♦      Most existing inkjets         contains: water, dye, surfactant, ♦       No odor ♦ Corrosive ♦ All IJ series ink      jets         humectant, and biocide.  ♦       Bleeds on paper ♦       Silverbrook EP 0771                       Modem ink dyes have high      water-  ♦       May strikethrough 658 A2 and related               fastness, light      fastness  ♦       Cockles paper patent applications               Aqueous, Water based      ink which typically ♦       Environmentally friendly ♦ Slow drying ♦      IJ02, IJ04, IJ21, IJ26        pigment contains: water, pigment, surfactant, ♦ No odor      ♦ Corrosive ♦       IJ27, IJ30                       humectant, and biocide. ♦        Reduced bleed ♦ Pigment may clog nozzles ♦        Silverbrook, EP 0771         Pigments have an advantage in ♦ Reduced wicking      ♦       Pigment may clog actuator 658 A2 and related               reduced      bleed, wicking and ♦ Reduced strikethrough mechanisms      patent applications         strikethrough.  ♦ Cockles paper ♦      Piezoelectric ink-jets            ♦       Thermal ink jets                                        (with significan       t            restrictions)        Methyl Ethyl MEK is a highly volatile solvent ♦ Very      fast drying ♦ Odorous ♦ All IJ series      inkjets        Ketone (MEK) used for industrial printing on ♦ Prints on        various substrates ♦       Flammable                             difficult surfaces such as      aluminum such as metals and plastics         cans.        Alcohol Alcohol based inks can be used ♦ Fast drying      ♦ Slight odor ♦ All IJ series ink jet              (ethanol, 2- where the printer must operate at ♦      Operates at sub-freezing ♦       Flammable                        butanol, and temperatures below the      freezing temperatures        others) point of water. An example of this is ♦ Reduced      paper cockle         in-camera consumer photographic ♦       Low cost                printing.        Phase change The ink is solid at room temperature, ♦ No      drying time-ink ♦ High viscosity ♦ Tektronix        hot melt        (hot melt) and is melted in the print head before instantly freezes on        the ♦ Printed ink typically has a `waxy`       feel piezoelectric inkjets         jetting. Hot melt inks are usually print medium ♦      Printed pages may `block` . 1989 Nowak USP         wax based, with a melting point ♦ Almost any print      medium ♦ Ink temperature may be above the 4,820,346               around 80° C.. After jetting the ink can be used curie      point of permanent magnets ♦ All IJ series inkjets                freezes almost instantly upon ♦ No paper cockle      occurs ♦       Ink heaters consume power                           contacting the      print medium or a ♦ No wicking occurs ♦ Long        warm-up time         transfer roller. ♦       No bleed occurs                         ♦       No strikethrough occurs        Oil Oil based inks are extensively used ♦       High solubility medium for ♦ High viscosity: this is a      significant . All IJ series ink jets         in offset printing. They have some dyes limitation for use in      inkjets, which         advantages in improved ♦ Does not cockle paper usually      require a low viscosity. Some         characteristics on paper (especially ♦ Does not wick      through short chain and multi-branched oils         no wicking or cockle). Oil soluble paper have a sufficiently low      viscosity.         dies and pigments are required.  ♦       Slow drying           Microemulsion A microemulsion is a stable, self      ♦ Stops ink bleed ♦ Viscosity higher than      water ♦       All IJ series ink jets                               forming emulsion      of oil, water, and ♦ High dye solubility ♦      Cost is slightly higher than water based         surfactant. The characteristic drop ♦ Water, oil, and      amphiphilic ink         size is less than 100 nm, and is soluble dies can be used .diamond-sol       id.       High surfactant concentration required      determined by the preferred ♦ Can stabilize pigment      (around 5%)         curvature of the surfactant. suspensions

Ink Jet Printing

A large number of new forms of ink jet printers have been developed to facilitate alternative ink jet technologies for the image processing and data distribution system. Various combinations of ink jet devices can be included in printer devices incorporated as part of the present invention. Australian Provisional Patent Applications relating to these ink jets which are specifically incorporated by cross reference include:

    ______________________________________                                         Australian                                                                                           Provisional                                                Number Filing Date Title                                                     ______________________________________                                         PO8066   Jul. 15, 1997                                                                              Image Creation Method and                                     Apparatus (IJ01)                                                             PO8072 Jul. 15, 1997 Image Creation Method and                                   Apparatus (IJ02)                                                             PO8040 Jul. 15, 1997 Image Creation Method and                                   Apparatus (IJ03)                                                             PO8071 Jul. 15, 1997 Image Creation Method and                                   Apparatus (IJ04)                                                             PO8047 Jul. 15, 1997 Image Creation Method and                                   Apparatus (IJ05)                                                             PO8035 Jul. 15, 1997 Image Creation Method and                                   Apparatus (IJ06)                                                             PO8044 Jul. 15, 1997 Image Creation Method and                                   Apparatus (IJ07)                                                             PO8063 Jul. 15, 1997 Image Creation Method and                                   Apparatus (IJ08)                                                             PO8057 Jul. 15, 1997 Image Creation Method and                                   Apparatus (IJ09)                                                             PO8056 Jul. 15, 1997 Image Creation Method and                                   Apparatus (IJ10)                                                             PO8069 Jul. 15, 1997 Image Creation Method and                                   Apparatus (IJ11)                                                             PO8049 Jul. 15, 1997 Image Creation Method and                                   Apparatus (IJ12)                                                             PO8036 Jul. 15, 1997 Image Creation Method and                                   Apparatus (IJ13)                                                             PO8048 Jul. 15, 1997 Image Creation Method and                                   Apparatus (IJ14)                                                             PO8070 Jul. 15, 1997 Image Creation Method and                                   Apparatus (IJ15)                                                             PO8067 Jul. 15, 1997 Image Creation Method and                                   Apparatus (IJ16)                                                             PO8001 Jul. 15, 1997 Image Creation Method and                                   Apparatus (IJ17)                                                             PO8038 Jul. 15, 1997 Image Creation Method and                                   Apparatus (IJ18)                                                             PO8033 Jul. 15, 1997 Image Creation Method and                                   Apparatus (IJ19)                                                             PO8002 Jul. 15, 1997 Image Creation Method and                                   Apparatus (IJ20)                                                             PO8068 Jul. 15, 1997 Image Creation Method and                                   Apparatus (IJ21)                                                             PO8062 Jul. 15, 1997 Image Creation Method and                                   Apparatus (IJ22)                                                             PO8034 Jul. 15, 1997 Image Creation Method and                                   Apparatus (IJ23)                                                             PO8039 Jul. 15, 1997 Image Creation Method and                                   Apparatus (IJ24)                                                             PO8041 Jul. 15, 1997 Image Creation Method and                                   Apparatus (IJ25)                                                             PO8004 Jul. 15, 1997 Image Creation Method and                                   Apparatus (IJ26)                                                             PO8037 Jul. 15, 1997 Image Creation Method and                                   Apparatus (IJ27)                                                             PO8043 Jul. 15, 1997 Image Creation Method and                                   Apparatus (IJ28)                                                             PO8042 Jul. 15, 1997 Image Creation Method and                                   Apparatus (IJ29)                                                             PO8064 Jul. 15, 1997 Image Creation Method and                                   Apparatus (IJ30)                                                             PO9389 Sep. 23, 1997 Image Creation Method and                                   Apparatus (IJ31)                                                             PO9391 Sep. 23, 1997 Image Creation Method and                                   Apparatus (IJ32)                                                             PP0888 Dec. 12, 1997 Image Creation Method and                                   Apparatus (IJ33)                                                             PP0891 Dec. 12, 1997 Image Creation Method and                                   Apparatus (IJ34)                                                             PP0890 Dec. 12, 1997 Image Creation Method and                                   Apparatus (IJ35)                                                             PP0873 Dec. 12, 1997 Image Creation Method and                                   Apparatus (IJ36)                                                             PP0993 Dec. 12, 1997 Image Creation Method and                                   Apparatus (IJ37)                                                             PP0890 Dec. 12, 1997 Image Creation Method and                                   Apparatus (IJ38)                                                             PP1398 Jan. 19, 1998 An Image Creation Method and                                Apparatus (IJ39)                                                             PP2592 Mar. 25, 1998 An Image Creation Method and                                Apparatus (IJ40)                                                             PP2593 Mar. 25, 1998 Image Creation Method and                                   Apparatus (IJ41)                                                             PP3991 Jun. 9, 1998 Image Creation Method and                                    Apparatus (IJ42)                                                             PP3987 Jun. 9, 1998 Image Creation Method and                                    Apparatus (IJ43)                                                             PP3985 Jun. 9, 1998 Image Creation Method and                                    Apparatus (IJ44)                                                             PP3983 Jun. 9, 1998 Image Creation Method and                                    Apparatus (IJ45)                                                           ______________________________________                                    

Ink Jet Manufacturing

Further, the present application may utilize advanced semiconductor fabrication techniques in the construction of large arrays of ink jet printers. Suitable manufacturing techniques are described in the following Australian provisional patent specifications incorporated here by cross-reference:

    __________________________________________________________________________     Australian                                                                       Provisional                                                                    Number Filing Date Title                                                     __________________________________________________________________________     PO7935                                                                               15-Jul-97                                                                            A Method of Manufacture of an Image Creation Apparatus                         (IJM01)                                                              PO7936 15-Jul-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM02)                                                              PO7937 15-Jul-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM03)                                                              PO8061 15-Jul-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM04)                                                              PO8054 15-Jul-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM05)                                                              PO8065 15-Jul-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM06)                                                              PO8055 15-Jul-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM07)                                                              PO8053 15-Jul-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM08)                                                              PO8078 15-Jul-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM09)                                                              PO7933 15-Jul-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM10)                                                              PO7950 15-Jul-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM11)                                                              PO7949 15-Jul-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM12)                                                              PO8060 15-Jul-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM13)                                                              PO8059 15-Jul-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM14)                                                              PO8073 15-Jul-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM15)                                                              PO8076 15-Jul-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM16)                                                              PO8075 15-Jul-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM17)                                                              PO8079 15-Jul-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM18)                                                              PO8050 15-Jul-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM19)                                                              PO8052 15-Jul-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM20)                                                              PO7948 15-Jul-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM21)                                                              PO7951 15-Jul-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM22)                                                              PO8074 15-Jul-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM23)                                                              PO7941 15-Jul-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM24)                                                              PO8077 15-Jul-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM25)                                                              PO8058 15-Jul-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM26)                                                              PO8051 15-Jul-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM27)                                                              PO8045 15-Jul-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM28)                                                              PO7952 15-Jul-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM29)                                                              PO8046 15-Jul-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM30)                                                              PO8503 11-Aug-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM30a)                                                             PO9390 23-Sep-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM31)                                                              PO9392 23-Sep-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM32)                                                              PP0889 12-Dec-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM35)                                                              PP0887 12-Dec-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM36)                                                              PP0882 12-Dec-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM37)                                                              PP0874 12-Dec-97 A Method of Manufacture of an Image Creation Apparatus                  (IJM38)                                                              PP1396 19-Jan-98 A Method of Manufacture of an Image Creation Apparatus                  (IJM39)                                                              PP2591 25-Mar-98 A Method of Manufacture of an Image Creation Apparatus                  (IJM41)                                                              PP3989 9-Jun-98 A Method of Manufacture of an Image Creation Apparatus                   (IJM40)                                                              PP3990 9-Jun-98 A Method of Manufacture of an Image Creation Apparatus                   (IJM42)                                                              PP3986 9-Jun-98 A Method of Manufacture of an Image Creation Apparatus                   (IJM43)                                                              PP3984 9-Jun-98 A Method of Manufacture of an Image Creation Apparatus                   (IJM44)                                                              PP3982 9-Jun-98 A Method of Manufacture of an Image Creation Apparatus                   (IJM45)                                                            __________________________________________________________________________

Fluid Supply

Further, the present application may utilize an ink delivery system to the ink jet head. Delivery systems relating to the supply of ink to a series of ink jet nozzles are described in the following Australian provisional patent specifications, the disclosure of which are hereby incorporated by cross-reference:

    ______________________________________                                         Australian                                                                       Provisional                                                                    Number Filing Date Title                                                     ______________________________________                                         PO8003   Jul. 15, 1997                                                                              Supply Method and Apparatus (F1)                            PO8005 Jul. 15, 1997 Supply Method and Apparatus (F2)                          PO9404 Sep. 23, 1997 A Device and Method (F3)                                ______________________________________                                    

MEMS Technology

Further, the present application may utilize advanced semiconductor microelectromechanical techniques in the construction of large arrays of ink jet printers. Suitable microelectromechanical techniques are described in the following Australian provisional patent specifications incorporated here by cross-reference:

    ______________________________________                                         Australian                                                                       Provisional                                                                    Number Filing Date Title                                                     ______________________________________                                         PO7943   Jul. 15, 1997                                                                              A device (MEMS01)                                           PO8006 Jul. 15, 1997 A device (MEMS02)                                         PO8007 Jul. 15, 1997 A device (MEMS03)                                         PO8008 Jul. 15, 1997 A device (MEMS04)                                         PO8010 Jul. 15, 1997 A device (MEMS05)                                         PO8011 Jul. 15, 1997 A device (MEMS06)                                         PO7947 Jul. 15, 1997 A device (MEMS07)                                         PO7945 Jul. 15, 1997 A device (MEMS08)                                         PO7944 Jul. 15, 1997 A device (MEMS09)                                         PO7946 Jul. 15, 1997 A device (MEMS10)                                         PO9393 Sep. 23, 1997 A Device and Method (MEMS11)                              PP0875 Dec. 12, 1997 A Device (MEMS12)                                         PP0894 Dec. 12, 1997 A Device and Method (MEMS13)                            ______________________________________                                    

IR Technologies

Further, the present application may include the utilization of a disposable camera system such as those described in the following Australian provisional patent specifications incorporated here by cross-reference:

    ______________________________________                                         Australian                                                                       Provisional                                                                    Number Filing Date Title                                                     ______________________________________                                         PP0895  Dec. 12, 1997                                                                             An Image Creation Method and Apparatus                          (IR01)                                                                       PP0870 Dec. 12, 1997 A Device and Method (IR02)                                PP0869 Dec. 12, 1997 A Device and Method (IR04)                                PP0887 Dec. 12, 1997 Image Creation Method and Apparatus                         (IR05)                                                                       PP0885 Dec. 12, 1997 An Image Production System (IR06)                         PP0884 Dec. 12, 1997 Image Creation Method and Apparatus                         (IR10)                                                                       PP0886 Dec. 12, 1997 Image Creation Method and Apparatus                         (IR12)                                                                       PP0871 Dec. 12, 1997 A Device and Method (IR13)                                PP0876 Dec. 12, 1997 An Image Processing Method and                              Apparatus (IR14)                                                             PP0877 Dec. 12, 1997 A Device and Method (IR16)                                PP0878 Dec. 12, 1997 A Device and Method (IR17)                                PP0879 Dec. 12, 1997 A Device and Method (IR18)                                PP0883 Dec. 12, 1997 A Device and Method (IR19)                                PP0880 Dec. 12, 1997 A Device and Method (IR20)                                PP0881 Dec. 12, 1997 A Device and Method (IR21)                              ______________________________________                                    

DotCard Technologies

Further, the present application may include the utilization of a data distribution system such as that described in the following Australian provisional patent specifications incorporated here by cross-reference:

    ______________________________________                                         Australian                                                                       Provisional                                                                    Number Filing Date Title                                                     ______________________________________                                         PP2370     Mar. 16, 1998                                                                              Data Processing Method and                                  Apparatus (Dot01)                                                            PP2371 Mar. 16, 1998 Data Processing Method and                                  Apparatus (Dot02)                                                          ______________________________________                                    

Artcam Technologies

Further, the present application may include the utilization of camera and data processing techniques such as an Artcam type device as described in the following Australian provisional patent specifications incorporated here by cross-reference:

    ______________________________________                                         Austral-                                                                         ian                                                                            Provis-                                                                        ional Filing                                                                   Number Date Title                                                            ______________________________________                                         PO7991                                                                               15-Jul-97                                                                               Image Processing Method and Apparatus (ART01)                     PO8505 11-Aug-97 Image Processing Method and Apparatus (ART01a)                              PO7988 15-Jul-97 Image Processing Method and Apparatus                        (ART02)                                                           PO7993 15-Jul-97 Image Processing Method and Apparatus (ART03)                 PO8012 15-Jul-97 Image Processing Method and Apparatus (ART05)                 PO8017 15-Jul-97 Image Processing Method and Apparatus (ART06)                 PO8014 15-Jul-97 Media Device (ART07)                                          PO8025 15-Jul-97 Image Processing Method and Apparatus (ART08)                 PO8032 15-Jul-97 Image Processing Method and Apparatus (ART09)                 PO7999 15-Jul-97 Image Processing Method and Apparatus (ART10)                 PO7998 15-Jul-97 Image Processing Method and Apparatus (ART11)                 PO8031 15-Jul-97 Image Processing Method and Apparatus (ART12)                 PO8030 15-Jul-97 Media Device (ART13)                                          PO8498 11-Aug-97 Image Processing Method and Apparatus (ART14)                 PO7997 15-Jul-97 Media Device (ART15)                                          PO7979 15-Jul-97 Media Device (ART16)                                          PO8015 15-Jul-97 Media Device (ART17)                                          PO7978 15-Jul-97 Media Device (ART18)                                          PO7982 15-Jul-97 Data Processing Method and Apparatus (ART19)                  PO7989 15-Jul-97 Data Processing Method and Apparatus (ART20)                  PO8019 15-Jul-97 Media Processing Method and Apparatus (ART21)                 PO7980 15-Jul-97 Image Processing Method and Apparatus (ART22)                 PO7942 15-Jul-97 Image Processing Method and Apparatus (ART23)                 PO8018 15-Jul-97 Image Processing Method and Apparatus (ART24)                 PO7938 15-Jul-97 Image Processing Method and Apparatus (ART25)                 PO8016 15-Jul-97 Image Processing Method and Apparatus (ART26)                 PO8024 15-Jul-97 Image Processing Method and Apparatus (ART27)                 PO7940 15-Jul-97 Data Processing Method and Apparatus (ART28)                  PO7939 15-Jul-97 Data Processing Method and Apparatus (ART29)                  PO8501 11-Aug-97 Image Processing Method and Apparatus (ART30)                 PO8500 11-Aug-97 Image Processing Method and Apparatus (ART31)                 PO7987 15-Jul-97 Data Processing Method and Apparatus (ART32)                  PO8022 15-Jul-97 Image Processing Method and Apparatus (ART33)                 PO8497 11-Aug-97 Image Processing Method and Apparatus (ART30)                 PO8029 15-Jul-97 Sensor Creation Method and Apparatus (ART36)                  PO7985 15-Jul-97 Data Processing Method and Apparatus (ART37)                  PO8020 15-Jul-97 Data Processing Method and Apparatus (ART38)                  PO8023 15-Jul-97 Data Processing Method and Apparatus (ART39)                  PO9395 23-Sep-97 Data Processing Method and Apparatus (ART4)                   PO8021 15-Jul-97 Data Processing Method and Apparatus (ART40)                  PO8504 11-Aug-97 Image Processing Method and Apparatus (ART42)                 PO8000 15-Jul-97 Data Processing Method and Apparatus (ART43)                  PO7977 15-Jul-97 Data Processing Method and Apparatus (ART44)                  PO7934 15-Jul-97 Data Processing Method and Apparatus (ART45)                  PO7990 15-Jul-97 Data Processing Method and Apparatus (ART46)                  PO8499 11-Aug-97 Image Processing Method and Apparatus (ART47)                 PO8502 11-Aug-97 Image Processing Method and Apparatus (ART48)                 PO7981 15-Jul-97 Data Processing Method and Apparatus (ART50)                  PO7986 15-Jul-97 Data Processing Method and Apparatus (ART51)                  PO7983 15-Jul-97 Data Processing Method and Apparatus (ART52)                  PO8026 15-Jul-97 Image Processing Method and Apparatus (ART53)                 PO8027 15-Jul-97 Image Processing Method and Apparatus (ART54)                 PO8028 15-Jul-97 Image Processing Method and Apparatus (ART56)                 PO9394 23-Sep-97 Image Processing Method and Apparatus (ART57)                 PO9396 23-Sep-97 Data Processing Method and Apparatus (ART58)                  PO9397 23-Sep-97 Data Processing Method and Apparatus (ART59)                  PO9398 23-Sep-97 Data Processing Method and Apparatus (ART60)                  PO9399 23-Sep-97 Data Processing Method and Apparatus (ART61)                  PO9400 23-Sep-97 Data Processing Method and Apparatus (ART62)                  PO9401 23-Sep-97 Data Processing Method and Apparatus (ART63)                  PO9402 23-Sep-97 Data Processing Method and Apparatus (ART64)                  PO9403 23-Sep-97 Data Processing Method and Apparatus (ART65)                  PO9405 23-Sep-97 Data Processing Method and Apparatus (ART66)                  PP0959 16-Dec-97 A Data Processing Method and Apparatus (ART68)                              PP1397 19-Jan-98 A Media Device (ART69)                        ______________________________________                                     

We claim:
 1. A micromechanical thermal actuator having a bend axis arranged to curve upon actuation, said actuator comprising:a first material having a first coefficient of thermal expansion; a serpentine heater element having a relatively lower coefficient of thermal expansion in thermal contact with said first material and adapted to heat said first material on demand; said serpentine heater element having a majority of its length perpendicular to the bend axis of the actuator enabling the heater element to be elongated upon heating so as to accommodate the expansion of said first material.
 2. An actuator as claimed in claim 1 wherein said serpentine heater element comprises a layer of poly-silicon.
 3. An actuator as claimed in either claim 1 or claim 2 wherein said first material is provided in a first layer and the actuator further comprises a second layer having a relatively higher coefficient at thermal expansion than said first layer, the heater element being in thermal contact with said first layer and said second layer such that on heating said heater element, said actuator moves from a first quiescent position to a second actuation position.
 4. An actuator as claimed in claim 3 wherein said heater element is sandwiched between said first layer and said second layer.
 5. An actuator as claimed in either claim 1 or claim 2 wherein the first material forms a layer and the heater element is embedded in the first material toward one surface of the layer.
 6. An actuator as claimed in claim 1 wherein said first material comprises polytetrafluoroethylene.
 7. An actuator as claimed in claim 3 wherein said second layer is selected from the group comprising silicon dioxide and silicon nitride. 